Liquid bearing for rotary apparatus

Abstract

A liquid bearing for use in rotary devices processing biological fluids is disclosed. The device has a stationary housing and a rotating cartridge. One end of the cartridge is rotatably connected to the housing. The other end is not directly connected to the housing, and, thus, is free to move laterally during rotation. The liquid bearing tends to recenter the free end of the cartridge during rotation.

I claim: 
     
       1. In combination: (a) a rotary device having (i) an outer stationary housing defining a cavity, the cavity having a longitudinal axis;   (ii) an inner cartridge having first and second ends and having a longitudinal axis of rotation passing through both ends, the cartridge being mounted for rotation within the housing so that the longitudinal axis of the housing and the axis of rotation of the cartridge are substantially co-linear, the first end of the cartridge being free of any direct attachment to the housing and having a tendency during rotation to be laterally displaced from the longitudinal axis of the housing;   (iii) a liquid bearing zone defined by (A) a rotating bearing surface at the first end of the cartridge substantially symmetrically located about the cartridge's axis of rotation and (B) a corresponding stationary bearing surface attached to the housing, substantially symmetrically located about the housing's longitudinal axis, and closely spaced from the rotating bearing surface; and     (b) biological fluid located between the two bearing surfaces; the bearing surfaces being spaced far enough apart so that during rotation a liquid bearing is created in the liquid bearing zone by the biological fluid and the bearing surfaces to provide hydrodynamic forces that tend to recenter the first end of the cartridge.   
     
     
       2. The combination of claim 1 wherein the rotating bearing surface is a concavity. 
     
     
       3. The combination of claim 2 wherein the stationary bearing surface is a convexity. 
     
     
       4. The combination of claim 2 wherein the concavity has a side surface and the side surface is at an angle greater than zero with respect to the axis of rotation. 
     
     
       5. The combination of claim 4 wherein the concavity has a shape selected from the group consisting of conical, frusto-conical, and hemispherical. 
     
     
       6. The combination of claim 1 wherein the liquid bearing zone is at the bottom of the rotary device. 
     
     
       7. The combination of claim 1 wherein the rotating bearing surface is a convexity. 
     
     
       8. The combination of claim 7 wherein the stationary bearing surface is a concavity. 
     
     
       9. The combination of claim 7 wherein the convexity has a side surface and the side surface is at an angle greater than zero with respect to the axis of rotation. 
     
     
       10. The combination of claim 9 wherein the convexity has a shape selected from the group consisting of conical, frusto-conical, and hemispherical. 
     
     
       11. The combination of claim 1 wherein the rotary device is a rotary membrane filter and the housing has an inner wall, the cartridge has an outer wall opposite the inner wall of the housing to define a gap therebetween, and a membrane is mounted on the outer wall of the cartridge or on the inner wall of the housing facing the gap. 
     
     
       12. The combination of claim 11 wherein the biological fluid is present in the gap and the cartridge can be rotated to produce a calculated Taylor number for the fluid in the gap greater than about 40. 
     
     
       13. The combination of claim 1 further comprising means to circulate the biological fluid between the two bearing surfaces. 
     
     
       14. The combination of claim 13 wherein the means to circulate the biological fluid comprises at least one passageway for the fluid having at least one terminal opening in the stationary bearing surface. 
     
     
       15. The combination of claim 1 wherein the stationary bearing surface may be moved longitudinally to vary the spacing between the two bearing surfaces. 
     
     
       16. The combination of claim 1 wherein the rotating bearing surface has a cylindrical shape. 
     
     
       17. The combination of claim 1 wherein at least part of the rotating bearing surface has the same diameter as the cartridge.